tint/test-runner: Split expectations for FXC and DXC

Change tint's `--fxc` flag to take the path of the FXC compiler DLL.
Have tint attempt to validate with both FXC and DXC if `--validate` is
passed.

Fix the 'dirsWithNoPassExpectations' logic which looks like it got
broken with the tint -> dawn merge. It also incorrectly applied
filepath.FromSlash() on windows.

Change-Id: I0f46aa5c21bc48a2abc48402c41f846aff4a8633
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/96800
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@chromium.org>

test/tint/statements/compound_assign/matrix/minus.wgsl.expected.fxc.hlsl

@@ -0,0 +1,21 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+RWByteAddressBuffer v : register(u0, space0);
+
+void tint_symbol(RWByteAddressBuffer buffer, uint offset, float4x4 value) {
+  buffer.Store4((offset + 0u), asuint(value[0u]));
+  buffer.Store4((offset + 16u), asuint(value[1u]));
+  buffer.Store4((offset + 32u), asuint(value[2u]));
+  buffer.Store4((offset + 48u), asuint(value[3u]));
+}
+
+float4x4 tint_symbol_2(RWByteAddressBuffer buffer, uint offset) {
+  return float4x4(asfloat(buffer.Load4((offset + 0u))), asfloat(buffer.Load4((offset + 16u))), asfloat(buffer.Load4((offset + 32u))), asfloat(buffer.Load4((offset + 48u))));
+}
+
+void foo() {
+  tint_symbol(v, 0u, (tint_symbol_2(v, 0u) - float4x4((0.0f).xxxx, (0.0f).xxxx, (0.0f).xxxx, (0.0f).xxxx)));
+}

test/tint/statements/compound_assign/matrix/plus.wgsl.expected.fxc.hlsl

@@ -0,0 +1,21 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+RWByteAddressBuffer v : register(u0, space0);
+
+void tint_symbol(RWByteAddressBuffer buffer, uint offset, float4x4 value) {
+  buffer.Store4((offset + 0u), asuint(value[0u]));
+  buffer.Store4((offset + 16u), asuint(value[1u]));
+  buffer.Store4((offset + 32u), asuint(value[2u]));
+  buffer.Store4((offset + 48u), asuint(value[3u]));
+}
+
+float4x4 tint_symbol_2(RWByteAddressBuffer buffer, uint offset) {
+  return float4x4(asfloat(buffer.Load4((offset + 0u))), asfloat(buffer.Load4((offset + 16u))), asfloat(buffer.Load4((offset + 32u))), asfloat(buffer.Load4((offset + 48u))));
+}
+
+void foo() {
+  tint_symbol(v, 0u, (tint_symbol_2(v, 0u) + float4x4((0.0f).xxxx, (0.0f).xxxx, (0.0f).xxxx, (0.0f).xxxx)));
+}

test/tint/statements/compound_assign/matrix/times-scalar.wgsl.expected.fxc.hlsl

@@ -0,0 +1,21 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+RWByteAddressBuffer v : register(u0, space0);
+
+void tint_symbol(RWByteAddressBuffer buffer, uint offset, float4x4 value) {
+  buffer.Store4((offset + 0u), asuint(value[0u]));
+  buffer.Store4((offset + 16u), asuint(value[1u]));
+  buffer.Store4((offset + 32u), asuint(value[2u]));
+  buffer.Store4((offset + 48u), asuint(value[3u]));
+}
+
+float4x4 tint_symbol_2(RWByteAddressBuffer buffer, uint offset) {
+  return float4x4(asfloat(buffer.Load4((offset + 0u))), asfloat(buffer.Load4((offset + 16u))), asfloat(buffer.Load4((offset + 32u))), asfloat(buffer.Load4((offset + 48u))));
+}
+
+void foo() {
+  tint_symbol(v, 0u, (tint_symbol_2(v, 0u) * 2.0f));
+}

test/tint/statements/compound_assign/matrix/times.wgsl.expected.fxc.hlsl

@@ -0,0 +1,21 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+RWByteAddressBuffer v : register(u0, space0);
+
+void tint_symbol(RWByteAddressBuffer buffer, uint offset, float4x4 value) {
+  buffer.Store4((offset + 0u), asuint(value[0u]));
+  buffer.Store4((offset + 16u), asuint(value[1u]));
+  buffer.Store4((offset + 32u), asuint(value[2u]));
+  buffer.Store4((offset + 48u), asuint(value[3u]));
+}
+
+float4x4 tint_symbol_2(RWByteAddressBuffer buffer, uint offset) {
+  return float4x4(asfloat(buffer.Load4((offset + 0u))), asfloat(buffer.Load4((offset + 16u))), asfloat(buffer.Load4((offset + 32u))), asfloat(buffer.Load4((offset + 48u))));
+}
+
+void foo() {
+  tint_symbol(v, 0u, mul(float4x4((0.0f).xxxx, (0.0f).xxxx, (0.0f).xxxx, (0.0f).xxxx), tint_symbol_2(v, 0u)));
+}